LTE PRACH DETECTION IN LTE TOOLBOX

Hi all,

I am a newbiee with lte toolbox and would really appreciate if some one could help me.

I am going through the prach detection function from lte toolbox; lteprach detect and i could not get around this code shown below.

% The following parameter specifies the fraction of the timing window at

% the end of the timing window for one preamble that will be considered

% as belonging to the next preamble and having a timing offset of zero.

% This effectively excludes timing offsets of above (1.0-deadzone) of the

% maximum and ensures detection of preambles with low timing offset where

% noise has caused the peak of the correlation to be slightly into the

% previous preamble's timing window. The value configured below corresponds

% to the duration of the main lobe of the autocorrelation of the PRACH.

% (zero is used for the case that NCS=0 as there is only one preamble

% per correlation.)

if (zcz~=0)

deadzone=info.SamplingRate/(info.NZC*info.SubcarrierSpacing)/zcz;

else

deadzone=0;

end

I would be great if someone could help me out.

I am following a textbook named LTE:From theorey to practise but could not find anything about it.

It would be great if any refernce is provided to understand this.

BR,

Sri

Answer 1

[prabhat kumar sharma]

Hello Sriharsha,

The code snippet you shared is related to the detection of Physical Random Access Channel (PRACH) preambles in LTE, specifically focusing on the concept of "deadzone" in the timing window for preamble detection. Let me break it down for you:Explanation of the Code

1. Deadzone Concept:

• The "deadzone" is a fraction of the timing window that is intentionally ignored during the detection of PRACH preambles. It helps to manage timing offsets that occur due to noise or other factors.
• This mechanism ensures that preambles with low timing offsets are detected accurately, even if the noise causes the correlation peak to shift slightly.

2. Variables:

• zcz: This is the zero-correlation zone length. It is a parameter related to the PRACH configuration that affects how preambles are detected.
• info.SamplingRate: The rate at which the signal is sampled.
• info.NZC: The length of the Zadoff-Chu sequence used in the PRACH preamble.
• info.SubcarrierSpacing: The spacing between subcarriers in the frequency domain.

3. Deadzone Calculation:

• The deadzone is calculated as info.SamplingRate / (info.NZC * info.SubcarrierSpacing) / zcz. This formula computes the fraction of the timing window that should be considered as part of the next preamble.
• If zcz is zero, indicating no zero-correlation zone, the deadzone is set to zero because there's only one preamble per correlation.

I hope it helps!